drivers/media/video/em28xx/: Fix undefined symbol error with CONFIG_SND=N

Without this you get undefined symbol errors with CONFIG_SND=N:

  ERROR: "snd_pcm_period_elapsed" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_pcm_hw_constraint_integer" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_pcm_set_ops" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_pcm_lib_ioctl" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_card_new" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_card_free" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_card_register" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
  ERROR: "snd_pcm_new" [drivers/media/video/em28xx/em28xx-alsa.ko] undefined!
Signed-off-by: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/media/video/em28xx/Kconfig

@@ -13,7 +13,8 @@ config VIDEO_EM28XX
 	  module will be called em28xx
 
 config VIDEO_EM28XX_ALSA
-	depends on VIDEO_EM28XX
+	depends on VIDEO_EM28XX && SND
+	select SND_PCM
 	tristate "Empia EM28xx ALSA audio module"
 	---help---
 	  This is an ALSA driver for some Empia 28xx based TV cards.